[dvorak365]

NTS is a form of moving the goalposts.

If you say "No X would do Y", and then after an X does Y move the goalposts to say "No true X would do Y", that's the fallacy.

If you simply stated in the first place that "No true X would do Y", then you're off the hook as long as your definition of "true X" doesn't apply to the particular X that did Y.

[aptwebapps]

To me, moving the goalposts and equivocation are the most pernicious fallacies in online discussions. They happen all the time, and often take more than minimal effort to dispute. It's also really easy to take them as made in bad faith.

[ewjordan]

> and often take more than minimal effort to dispute

This is where all ability to have a rational discussion breaks down in many cases, especially when people care a lot about their initial opinions.

Take an issue like evolution. You start with a source like https://www.khanacademy.org/science/biology/her/evolution-an..., which outlines a pretty good case for how evolution is supported by today's evidence. It gives plenty of lines to follow if you're curious to dig deeper, and absent other factors most people would just see it as a boring science thing that's probably true and they don't care much about.

But because some people are bothered by the idea, they've spent a lot of time thinking up objections. A whole lot of time. See https://en.wikipedia.org/wiki/Objections_to_evolution for summaries of just some of the complaints that people have come up with. These have all been thoroughly demolished, of course, but to do so often involves a lot of really labor-intensive science.

As far as science goes, that's all good - it's great to be detailed and thoroughly justify every piece of a theory, chasing any loose ends down at any cost. It's part of the job description.

But casual debate about the issue is devastatingly difficult, even if everyone is acting in good faith. All someone that has a problem with evolution has to do is throw out three or four big complaints (the eye! carbon dating! transitional fossils! micro vs macro-evolution!) and all of a sudden a proper response to their 3 minute "gotcha" attempt means a good half hour sourcing high quality rebuttals and summarizing them in the thread. Which will likely each bring up three or four points which the anti-evolution person can quibble with (and they'll be able to do so quickly). Assuming you make it through that gauntlet and the person accepts that you've shot down those points, a list of ten more fresh "problems", each of which requires detailed research and attention to shoot down, is a low-effort Google search away (say https://www.evolutionnews.org/2012/07/what_are_the_to_1/), so you can get "yeah, but!"-ted into oblivion until you're just not up to the task of responding anymore, even though you absolutely could address every complaint without difficulty, if you had the time.

Like you said, moving the goalposts. When you have an almost limitless sea of low-effort objections to draw from via Google (which you do, about almost anything, as long as a lot of people have spent time coming up with them), it's easy to put up a shitscreen so thick that nobody can ever break through, and not even realize that you're acting badly.

I know that rationalists very strongly believe that with enough good-faith discussion everyone's beliefs should ultimately align, and there should never be such a thing as agreeing to disagree, but I fear that in many cases the relaxation time to that state is prohibitively long.